Question

what is the composition of cement​

Answer 1

Explanation:

Composition of cement. Portland cement is manufactured by crushing, milling and proportioning the following materials: Lime or calcium oxide, CaO: from limestone, chalk, shells, shale or calcareous rock. Silica, SiO2: from sand, old bottles, clay or argillaceous rock.

Calcium oxide (lime): Ca0

Aluminum oxide (alumina): Al2O3

Silicon dioxide (silica): SiO2

Iron oxide: Fe2O3

Answer 2

Answer:

Chemical shorthand

Because of the complex chemical nature of cement, a shorthand form is used to denote the chemical compounds. The shorthand for the basic compounds is:

Compound

Formula

Shorthand form

Calcium oxide (lime)

Ca0

C

Silicon dioxide (silica)

SiO2

S

Aluminum oxide (alumina)

Al2O3

A

Iron oxide

Fe2O3

F

Water

H2O

H

Sulfate

SO3

S

Chemical composition of clinker

The cement clinker formed has the following typical composition:

Compound

Formula

Shorthand form

% by weight1

Tricalcium aluminate Ca3Al2O6 C3A 10

Tetracalcium aluminoferrite Ca4Al2Fe2O10 C4AF 8

Belite or dicalcium silicate Ca2SiO5 C2S 20

Alite or tricalcium silicate Ca3SiO4 C3S 55

Sodium oxide Na2O N )

)Up to 2

Potassium oxide K2O K

Gypsum CaSO4.2H2O CSH2 5

Representative weights only. Actual weight varies with type of cement.

Source: Mindess & Young

Properties of cement compounds

These compounds contribute to the properties of cement in different ways

Tricalcium aluminate, C3A:-

It liberates a lot of heat during the early stages of hydration, but has little strength contribution. Gypsum slows down the hydration rate of C3A. Cement low in C3A is sulfate resistant.

Tricalcium silicate, C3S:-

This compound hydrates and hardens rapidly. It is largely responsible for portland cement’s initial set and early strength gain.

Dicalcium silicate, C2S:

C2S hydrates and hardens slowly. It is largely responsible for strength gain after one week.

Ferrite, C4AF:

This is a fluxing agent which reduces the melting temperature of the raw materials in the kiln (from 3,000o F to 2,600o F). It hydrates rapidly, but does not contribute much to strength of the cement paste.

By mixing these compounds appropriately, manufacturers can produce different types of cement to suit several construction environments.